The url-downloader proxy has been configured to allow HTTPS (CONNECT) requests, to port 443 only, and as before, only from hosts in the Wikimedia network, and no requests to hosts within the Wikimedia network.

No, but that seems unrelated to this bug. Access to Wikimedia hosts was and remains blocked, for security reasons. We may be able to open it up to specific destinations to resolve bug 42473, but that requires additional work, and is not blocked on this ticket.